Just when I thought everything was sorted on the 05 320i, the air-conditioning started playing up. Sometimes - more often than not - when the car is started there is no cooling of the ventilation air. When it first happened I had the pressure tested and it measured perfect with no leaks in the system.

The system works, either 100% or not at all...so, next I took the car to BMW and the service man said he had seen it before but as far as he could tell it meant replacing either the compressor or the climate control computer. Both which cost the price of two kidneys & a lung.

An independent a/c specialist told me its likely the "compressor control valve" that has become intermittent or sticky, however they don't replace the valve separately but would install a new or recon compressor (also at a hefty cost)

I have since figured out a way to "fix" the cooling is while driving, to gear
the car down until the engine revs at 5500-6000 rpm and keep it there for a few seconds. Usually then the cooling returns and works perfectly until the engine is switched off.

Has anyone seen this before and what should be done??
Please comment...

I would certainly try that. The reason why it sounded like a clutch was that at high-revs the A/C begain to work (the speed of the pulley causing the clutch to engage was my thinking) but it still sounds electrical to me. Again, higher engine speed and compressor speed could cause a sticking valve like this to go over-centre and engage.

Hi guys i thought after doing a search i'd revive this thread rather than start a brand new one.

I went to get my air con done by a local bmw specialist. The technician said he noticed when turning the air con on and off that the compressor was still running when off. He said that it seemed that the clutch on the compressor wasn't engaging. I this right or does it sound as if it relates to the issue the guys in this thread were having previously?

If it means a replacement compressor then thats fine but i'd rather try the valve first.